A fabrication phase of a semiconductor device can include a process that subjects the semiconductor device to a potential gradient, or induces a charge on the surface of the semiconductor device. In some cases, high energy electrically charged particles (ions), associated with such a process can in turn enter layers of the semiconductor device and get trapped inside such layers. Trapped charges inside the layers can in turn adversely affect operating characteristics of the semiconductor device, such as high variation of corresponding threshold voltages, and in extreme cases can cause breakup of internal structures/layers of the device, rendering the device non-functional.
Various methods and apparatus for providing a discharge path for the charges injected inside the various layers of the semiconductor device during, for example, the plasma etching phase, have been devised. Such semiconductor devices can include metal-oxide-semiconductor (MOS) field effect transistors (FETs), and particularly to MOSFETs fabricated on silicon-on-insulator (SOI) and silicon-on-sapphire (SOS) substrates.
In particular, methods and apparatus for providing a discharge path to layers of an SOI device fabricated on a low resistivity substrate use a combination of an active diode and/or a junction diode. Such diodes are used so as to not affect normal operation of the semiconductor device fitted with the discharge path. In cases where a high resistivity substrate is used to fabricate the SOI device, it may be desirable to provide a simpler, more compact, and yet effective discharge path.